A known prior art support device for a plurality of wafers, shown in FIGS. 1A and 1B, is a support device for a plurality of wafers, the support device 10 being adapted to be loaded into a heat treatment oven, the support device 10 having a central axis, the support device 10 including:
three uprights 30, 31 and 32 extending substantially parallel to the central axis,
a plurality of series of support members 35 spaced along the central axis, each series of support members 35 comprising three support members 40, 41 and 42 adapted to support one wafer W of the plurality of wafers and extending in different essentially longitudinal directions transverse to the central axis, each support member 40, 41 and 42 being mounted directly on a separate upright.
Accordingly, a heat treatment step consists in positioning a support device 10 containing a plurality of wafers W in a vertical heat treatment oven (not shown). Each series of support members 35 of the support device 10 includes three support members 40, 41 and 42, the function of which is to hold a wafer W in a horizontal position. FIG. 1B shows the positioning of a wafer W relative to the support members 40, 41 and 42. The support members are mounted directly on separate uprights 30, 31 and 32 and the disposition of the support members 40, 41 and 42 is adapted to ensure that a wafer W is held in a stable equilibrium position. Inside the vertical heat treatment oven, heating elements are disposed around a quartz tube into which the support device 10 is inserted. The wafers disposed horizontally in the support device 10 are heated radially by the heating elements. However, the support members 41 and 42 block some of the radiant flux during a heat treatment step and a locally heterogeneous temperature field is observed over the volume of the wafer W at the level of the support members 41 and 42, as shown in FIG. 2 (the shaded area symbolizing the flow of heat in the vicinity of the support member 41).
If the requirements in terms of homogeneous heat treatment are imperatives, such a temperature gradient is not acceptable.
Moreover, a homogeneous temperature of the wafers during a heat treatment step is required when depositing or forming thin layers of materials having a highly uniform thickness.